1. Field of the Invention
The present invention generally relates to implantable medical devices. More particular, the invention relates to an implantable device with an improved mechanism for connection of a lead to the implantable device. Still more particularly, the invention relates to an implantable device that provides a positive indication that the lead has been properly connected to the device.
2. Background of the Invention
Many patients require an implantable medical device for any one of a variety of reasons. Many cardiac patients, for example, require an implanted pacemaker or defibrillator to assist the heart to beat properly. Other patients may benefit from an implanted nerve stimulator or drug delivery device. The present invention is described with respect to an implantable cardiac pacemaker, with the understanding, however, that the invention is useful in the context of many other types of implantable devices.
A typical implantable pacemaker generally comprises a hermetically-sealed electronics assembly and one or more flexible "leads" that electrically connect the assembly to the heart. The components of the assembly are enclosed in a housing commonly referred to as the "can." The leads contain electrical conductors that transmit signals generated inside the can to the heart to stimulate the cardiac tissue to beat. One end of the lead (the "proximal" end) mates with the pacemaker header, while the other end (the "distal" end) is routed into an internal chamber of the heart. The distal end of the leads includes one or more electrodes that make direct electrical contact with the tissue of the heart and/or blood within the heart. The leads can be any desired length, but generally are between 18 and 30 inches long. With this configuration, the can, which typically is small enough to fit in one's palm, can be positioned in any convenient location within the chest cavity and not necessarily immediately adjacent the heart. The distal end of the lead is routed along a convenient path, such as through an artery or vein, into one of the four chambers of the heart. Once inside a chamber, an electrode on the distal end of the lead is then attached to the internal lining, or myocardium, of the heart. Then, the can is positioned in the chest cavity and the surgeon connects the lead, or leads, to the can.
One concern that surgeons face when implanting a pacemaker in a patient is ensuring that the lead is properly inserted in the header, and thus electrically connected to the can. The proximal end of the lead, the end that connects to the can, typically includes a conductive metal member that is inserted into a "header" portion of the can. The header is normally constructed of a transparent, biocompatible material and includes a receptacle for receiving the proximal end of the lead. The header's electrical contacts within this receptacle connect to circuitry in the can by one or more wires. In the presence of body fluids present during surgery, it can be difficult for a surgeon to determine whether the lead has been completely inserted into the header. If the lead is not fully inserted into the header, the pacemaker may function erratically or not function at all.
Thus, it would be desirable to develop an implantable medical device, such as a pacemaker, that provides the surgeon a positive indication of proper lead insertion into the device. Such a device would give the surgeon increased confidence that the lead has been effectively mated with the pacemaker. Despite the significant advantages that could be offered by such a device, to date, no such implantable device connection is known to exist.